1. Field of the Invention
This invention relates generally to means for protecting an eye during surgery, and more particularly to techniques for shielding the retina from damaging high energy light during eye surgery.
2. Description of the Prior Art
Many kinds of eye surgery benefit from covering the eye during at least a portion of the operation. Cataract surgery is an example. A cataract is a clouding which occurs in the crystalline lens or lens capsule, which obstructs light passage.
Surgical techniques exist for the removal of cataracts from the eye. If the cataracts are severe enough, the original natural lens can be removed and replaced with a substitute intraocular lens. An incision is made at the junction (i.e., the limbus) of the cornea with the remainder of the eyeball, which is covered with a tough coating (i.e., the sclera) over the remainder of the eye. The cataract can be totally removed by applying a cryoprobe (freezing). Alternatively, the cataract can be removed by opening the anterior lens capsule; the nucleus of the cataract can then be manipulated out by a conventional pressure-counter pressure technique, or by use of a hollow vacuum pump-operated aspiration needle with ultrasound attachment to break up the nucleus into fine pieces that will fit through the needle. The cataract is then sucked out in the same manner as a vacuum cleaner operates.
A light source is used to provide light for illuminating the anterior segment of the eye upon which surgery is being performed. Best lighting is achieved by directing the light beam substantially perpendicular to the cornea. Disadvantages, however, exist with present lighting techniques. It is believed that intense and prolonged exposure of the retina to the light source may cause delay in recovery of the visual acuity of the eye. Further, it is suspected that present lighting techniques may cause permanent eye damage which sometimes results from eye surgery using a conventional operating microscope.
Attempts have been made to attenuate light received by the retina. One approach uses side lighting; several light sources are placed around the periphery of the eye, to shine in through the cornea toward the lens at an angle away from the perpendicular to the cornea. However, side lighting has the significant disadvantage of interfering shadows being cast by the surgeon's fingers, hands and instruments as all are moved during surgery. These shadows interfere with the vision of the surgeon.
Another attempted solution has been to place filters between the light source and eye. However, it is not known exactly which filters are required to prevent retina injury.
Protective shields for placing directly on the eyeball have been devised for use in plastic surgery. The eyeball is totally covered with the opaque shield to protect it from injury while surgery is performed on eye lids. However, the shield is not used for eye surgery because it totally obscures those regions of the eyeball upon which an operation is to be performed.